1. Field of the Invention
The present invention relates to a thin film magnetic head which performs a magnetic recording operation in a perpendicular recording scheme and a manufacturing method thereof, and to a magnetic head apparatus and a magnetic disk apparatus.
2. Description of the Related Art
In recent years, the surface recording density of a magnetic disk apparatus has been considerably improved. In particular, the surface recording density of a magnetic disk apparatus has recently reached 160 to 200 giga bytes/platter and will further robustly exceeds this value. With this increase, an improvement in performance of a thin film magnetic head has been demanded.
Roughly classifying the thin film magnetic head based on recording schemes, there are a longitudinal recording scheme which records information in an in-recording-surface (longitudinal) direction of a magnetic disk and a perpendicular recording scheme which records information in a vertical direction of a recording surface. Of these schemes, a thin film magnetic head based on the vertical recoding scheme can realize the recording density which is greatly higher than that of the longitudinal recording scheme, and a magnetic disk recorded by the thin film magnetic head is hardly affected by heat wobbles. Therefore, the perpendicular recording scheme is expected as compared with the longitudinal recording scheme. A thin film magnetic head based on the conventional perpendicular recording scheme is disclosed in specifications of, e.g., U.S. Pat. No. 6,504,675, U.S. Pat. No. 4,656,546, U.S. Pat. No. 4,672,493, Japanese Patent Application Laid-open No. 2004-94997 and others.
Meanwhile, when recording data in an area at an inner periphery or an outer periphery of a magnetic disk, by using a thin film magnetic head based on the perpendicular recording scheme, a magnetic pole end portion arranged at the side of a medium opposing surface (which will be also referred to as an air bearing surface or ABS) facing the magnetic disk inclines at a given angle (Skew Angle) with respect to a track on which data is recorded.
If the write capability is high in a magnetic head based on the perpendicular recording scheme (a perpendicular magnetic recording head: which will be referred to as a “PMR” hereinafter), there may occur a problem which is a so-called write blur by which unnecessary data is recorded between adjacent tracks due to generation of this skew angle. When this write blur is produced, detection of a servo signal or an S/N ratio of a reproduction waveform is adversely affected. Thus, in a conventional PMR, a magnetic pole end portion on the ABS side in a main magnetic pole film has a bevel shape whose width is gradually narrowed along one direction (see Japanese Patent Application Laid-open No. 2003-242607 and Japanese Patent Application Laid-open No. 2003-203311).
As the PMR having the magnetic pole end portion formed into a bevel shape, there is known one comprising a lower yoke film, a main magnetic pole film having a bevel-shaped magnetic pole end portion, and a write shield layer facing the main magnetic pole film with a recording gap film sandwiched therebetween on the ABS side. In this type of PMR, one having a narrower track width is demanded in order to improve the recording density. Further, it is desirable to provide the excellent overwrite characteristics and prevent data from being overwritten on another data recorded on a magnetic disk. Accordingly, providing a configuration in which the lower yoke film is arranged close to the ABS is desirable.
In this type of PMR, however, since the main magnetic pole film is formed after the lower yoke film, the lower yoke film is affected and a neck height appears when forming the main magnetic pole film with the magnetic pole end portion having a bevel shape, and a part having a narrow width corresponding to a track width is extended by a length corresponding to the neck height part, resulting in the possibility of shifting from a designed length.
In order to avoid the influence by shifting of this neck height, the lower yoke film must be formed apart from the ABS, and it is difficult to increase a magnetic charge (which is also referred to as a magnetic volume) at a part close to the ABS. Therefore, the conventional PMR has a problem that providing the excellent overwrite characteristics is difficult.